There are many traffic laws in the United States which may vary from one state to another, which residents of each state may have come to take for granted. Is there any sort of motorists' guide to these laws, and where and how they vary?

There are other things like whether insurance is mandatory, possibly what paperwork you must have with you, whether you must have license plates front and back. Possibly seatbelt laws, etc.
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hippietrailSep 6 '11 at 19:26

@hippietrail - Usually, front/back license plate laws only apply for the state in which the vehicle is registered. So, that's not so much a concern for travelers. Seatbelt laws and personal/vehicle documentation availability could be important though.
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IsziSep 6 '11 at 19:51

I was just remembering the time in 1990 when I was driving through Illinois in a California registered car with only a rear plate and Mr police man mentioned that that must be OK in California but went easy on me, possibly due to being a foreigner with short hair at the time (-:
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hippietrailSep 6 '11 at 20:08

I would also add Carseats and booster seats laws. Some states go by height, some by age the others by weight.
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VitalikDec 18 '13 at 20:46

Right turn is permitted on Red unless specifically prohibited, Right turn arrow indicated or in New York City.

Left turn on Red one way to one way and otherwise is prohibited, unless seen as common practice by the locals.

U-Turn permitted where left turn is permitted unless specifically prohibited or crossing a solid double line.

Passing in the Right lane: Permitted on a multilane road

Left lane non-passing usage is permitted unless otherwise posted.

Cellphone usage. Varies widely from state to state from Fully Prohibiting usage of handheld devices such in New York, Connecticut to being a secondary offense, to not being an offense.

My general advise to you is watch the locals and follow what they do. Because aside from real laws there are Dumb Laws, which also include traffic laws such as required honking while passing a car in Virginia. Is that enforced? Probably not but law is still on the books.

"Left turn on Red one way to one way and otherwise is prohibited" Are you saying left turn on red one way to one way is prohibited? This is hardly the "common practice". According to the linked-to Wikipedia article, left turn on red from one way to one way is legal in 42 states. That's almost all of them.
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user102008Dec 18 '13 at 22:38